We plan to study the control of glycogen synthesis by isolated rat hepatocytes. We have discovered that glutamine and asparagine and some other amino acids increases glycogen synthesis from many substrates, especially from lactate. We wish to determine the mechanism of this effect. There is evidence for the occurrence of a futile cycle between glycogen and glucose in liver. We will measure the rate of such cycling and assess its role in the regulation of glycogen metabolism. We have found that the addition of the calcium ligand EGTA stimulates the synthesis of glycogen from glucose by rat hepatocytes. We will explore the role of cell calcium in the control of glycogen metabolism. Effects of potassium, insulin, and corticosteroids on glycogen metabolism will be studied.